Continuous enveloping of different products is an art which has been well known for a long time and which comprises a double apron feeder, with widths of various envelopes, inside of which, the product to be enveloped is inserted.
At present, due to marketing reasons, and also for sanitary reasons, bulk supplies are very scarce, not only those consisting of solid or pasty food products but also including those liquids which are not adequately packed.
The enveloping rate depends not only on the product. For example, the easiest one, because of particle size and external configuration, is sugar, though other factors are redundant in this process, as is the case of the characteristics of the material of the envelope which is normally plastic or paper laminate, the latter being generally plastified.
This material is bonded by means of the contact of the bevelled edges of triangular internal section, rollers which are parallel to each other and equipped with opposed rotation direction.
These cylinders normally comprise an electrical resistance thermal system, coactively rotational with the roller, fixedly attached, and consequently providing an intermediate heating rotational body: "Improvements In The Thermowelding Device", MU 9303010, of the present solicitant.
The continuous production line of envelopes which passes through at variable rate between both welding cylinders, varies in speed depending on these circumstances related to the materials used in the envelope and product to be enveloped.
According to economical reasons, it is useful to envelope the maximum possible number of envelopes, and this includes the possibility of bordering the acceptable temperature limits, either due to the more or less heat degradable type of product, or due to the envelope, which may become deformed by the effect of the heat, or to both reasons.
Up to the present, no solution to this problem is known other than that which plays with a number of rejections of envelopes allowing the profitability of this rise in temperature, the excess of the cooling time, etc.
On the other hand, the time of permanence in the normal running rate situation of the resistors, affects the economical efficiency of the machine after the stoppages, due to breakdowns, to offset of the envelopes during the vertical and horizontal cutting of the laminates, to misalignments of the latter, to product feeding problems and to a large etc.
It is recommended in all these cases to disconnect the resistors during the stoppage time, since the detection period for reheating by the thermostat is preset for the thermal cylinder when in operation not when stopped, this variation being sufficient for the generation of wastes in the production head, once it has recommenced.